The present invention relates to a semiconductor device comprising a dummy diffusion layer region and a dummy gate electrode which are unnecessary for actual circuit operation and a producing method of the semiconductor device.
Recently, particularly in a logic LSI (Large Scale Integrated Circuit), a part where transistors are arranged densely and a part where they are isolated from one another are present together in a LSI chip. Such a difference in density of the transistor arrangement influences the process of the size of a transistor gate electrode, for example, lithography and etching, and irregularity in the size of the gate electrodes after the process is thereby increased. In addition, a stacked interlayer insulation film is made flat by employing the technique of CMP (Chemical-Mechanical Polishing) after forming the transistors, but the thickness of the flat interlayer insulation film largely depends on the difference in density of the transistor arrangement in the substrate.
In consideration of this point, the technique of suppressing irregularity in the process by uniformly arranging dummy gate electrodes over a chip which are unnecessary for the actual LSI operation has been variously proposed.
However, a problem arises that if the dummy gate electrodes, which are unnecessary for the actual LSI operation, are kept in the floating state, they make the LSI operation unstable. In addition, another problem also arises that if the electric potential of the dummy gate electrodes is fixed to any portion in order to avoid the floating state, the wiring area is increased and the area of the chip is also increased.